Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.33	4.780%	$252.8656	$252.87	$252.85	$252.90
Purchase #2	$98.35	11.442%	$109.6032	$109.60	$109.60	$109.60
Purchase #3	$147.50	12.871%	$166.4847	$166.48	$166.50	$166.50
Purchase #4	$33.49	11.190%	$37.2375	$37.24	$37.25	$37.20
Purchase #5	$88.71	10.102%	$97.6715	$97.67	$97.65	$97.70
Purchase #6	$117.28	13.528%	$133.1456	$133.15	$133.15	$133.10
Purchase #7	$130.90	6.480%	$139.3823	$139.38	$139.40	$139.40
7 purchase totals =	$857.56		$936.3904	$936.39	$936.40	$936.40